Self-sealing tires with sealants applied to the inner surfaces thereof have been known as puncture resistant pneumatic tires (hereinafter, pneumatic tires are also referred to simply as tires). Sealants automatically seal puncture holes formed in such self-sealing tires. Various studies on sealants have been made.
For example, sealants have been studied which incorporate a low molecular weight polymer, have an improved tackifier content, or contain a large amount of oil or plasticizers to increase adhesion so that they exhibit an improved air sealing effect on punctured tires. Although such methods improve adhesion and air sealing, they reduce elastic modulus and also lead to a decrease in degree of crosslinking, with the result that the sealants flow during high-speed running.
Specifically, such methods will lead to an event where, when the sealants become hot during high-speed running, the elastic modulus is reduced so that the rubber can easily flow, and thus the sealants located in the middle of the tires will flow, resulting in an insufficient amount of the sealants located in desired positions in the width direction.
Sealants are also proposed which contain EPDM and polyisobutylene and are to be crosslinked using quinoid compounds. However, such sealants have problems such as a reduced degree of crosslinking of EPDM due to the quinoid crosslinking and the risk of flowing of the sealants during high-speed running. Furthermore, sealants are usually prepared by mixing with extruders or the like and are required to have processability, productivity, and other properties in the production of self-sealing tires. Therefore, there is a need for sealants that are excellent in properties including adhesion, sealing performance, fluidity, and processability.